This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: University of Birmingham scientists have developed a new material that changes from a gel to a liquid-like state under ultraviolet light and can be rebuilt using heat or dismantled by acid. Publishing their discovery in Journal of the American Chemical Society, the researchers described how they created the first multi-responsive gel built from "foldamers"—synthetic molecules that fold into defined shapes and can be assembled, disassembled and reassembled on demand.
Their discovery could ultimately help scientists design smart sensors, switchable catalysts and materials that capture and release selected molecules on demand. The material changes from a solid-like gel into a flowing, liquid-like state when exposed to ultraviolet light. Heating restores the gel, while acid provides a separate way to break down its molecular network.
Researchers from Birmingham's School of Chemistry also converted the material into a water-containing hydrogel without disrupting the molecular connections that hold it together. The work brought together expertise in designing new gels, led by Dr. Sarah Pike; supramolecular chemistry, led by Dr.
Chiara Arno; and atomic-level structure characterization, led by Dr. Pike said, "A very small change in molecular shape translates into a visible change in the whole material—demonstrating how carefully designed molecular components can give us control over the behavior of a bulk gel. "The research is at a fundamental stage, but the ability to program more than one response into the same material could ultimately inform the design of smart sensors, switchable catalysts and materials that capture and release selected molecules on demand." In the new material, helical foldamer molecules are joined by palladium ions, which act as four-way molecular connectors.
Together, they form an extended network that traps liquid and gives the material its gel-like properties. Ultraviolet light changes the shape of light-sensitive units within the foldamers. Although this change occurs at the scale of individual molecules, it is amplified across the network until the entire gel loses its solid-like structure, while heating allows the network to form again.
Acid acts through a different mechanism, disrupting the connections between the foldamers and the palladium ions. Arno said, "Supramolecular materials are assembled using reversible interactions rather than permanent chemical bonds. That gives us an opportunity to create materials that are robust under normal conditions but can be reorganized or dismantled when we apply the right signal.
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